#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int n = 0;
	scanf("%d", &n);
	int i = 0;
	double a = 1;
	double b = 2;
	double c = 0;
	double sum = 0;
	for (i = 1; i <= n; i++)
	{
		sum += (a/b);
		c = a;
		a = b;
		b = b + c;
	}
	printf("%.2lf", sum);
	return 0;
}